This invention relates to a method to prepare phenol from the products of decomposition (cleavage) of cumene hydroperoxide. Various decomposition product components, such as acetone, unreacted cumene, and alpha methyl styrene are removed by traditional distillation, leaving crude phenol. The method of this invention improves clarity of the resultant phenol, when dispersed in water.
The process for preparing cumene hydroperoxide for use as precursor feed for this invention can be by any of the known prior art processes, such as that described in U.S. Pat. No. 3,907,901, hereby incorporated by reference. Various distillation methods to separate the various components resulting from the cleavage of cumene hydroperoxide may be used, such as the teaching, which includes a method of treating crude phenol with alkaline hydrogen peroxide to remove mesityl oxide and its precursor impurities, described in U.S. Pat. No. 2,971,893, hereby incorporated by reference. Also see column 1 of U.S. Pat. No. 4,532,012 hereby incorporated by reference, in toto.
The test for clarity in water of phenol has been called the water light transmission (WLT) or water solubility test, described at column 1, lines 52-59, of U.S. Pat. No. 2,910,511, hereby incorporated by reference in toto.
The preferred prior art method to prepare crude phenol by fractional distillation from the product of decomposition of cumene hydroperoxide is shown in FIG. 1. Cumene, fresh and recycled, is fed through line 20 to an oxidizer 21 to form cumene hydroperoxide (CHP). CHP is fed to a decomposer 22 wherein CHP cleavage products result and some unreacted cumene is recycled. The remaining products are stored in crude storage 23 then fractionally distilled in a series of columns 24, 25, 26 and 27 as shown. The first distillation 24 removes acetone for further refining and sale. The second distillation 25 removes cumene for recycle to oxidizer feed. The third distillation 26 removes alphamethyl styrene (AMS) for further processing. The final column 27 produces phenol product overhead and takes organic residue from the bottom. This invention involves operation of the final phenol distillation column.
By external reflux ratio herein is meant overhead condensed liquid returned to the column top (reflux) flow rate divided by liquid overhead take-off flow rate.